The present invention generally relates to inks, and more particularly to UV curable inks.
UV curable inks are quick-curing inks and therefore are advantageous for use in continuous-type processes in which subsequent treatment of an ink-printed substrate is involved. A number of UV curable inks are known. For example, U.S. Pat. No. 4,271,258 discloses a photopolymerizable ink composition containing acrylate resin, methacrylate monomer or oligomer, acrylate monomer or oligomer, photoinitiator, and a particular type of an epoxy resin. U.S. Pat. No. 5,391,685 discloses a UV curable ink having an isocyanate compound added thereto. U.S. Pat. No. 5,391,685 contends that the ink disclosed therein is particularly well suited for printing on slightly adhesive plastic bases, such as those made of polyoxymethylenes and polypropylenes.
Screen printing on spherical surfaces such as golf balls can be difficult. As a result, pad printing customarily is used for marking golf ball surfaces. However, many of the known UV curable inks are not well suited for pad printing due to difficulties in transferring the ink from a pad to a substrate. Furthermore, UV curable inks that can be pad printed have not been found suitable for use on golf balls. More specifically, when applied to a golf ball, these inks are not sufficiently durable (impact resistant) to withstand multiple blows by a golf club.
It would be useful to obtain a highly durable UV curable ink which has favorable pad transfer properties when used for printing indicia on surfaces such as a curved and dimpled surface of a golf ball, and which provides an image having good durability.
An object of the invention is to provide a new and improved UV curable ink.
Another object of the invention is to provide a UV curable ink which is particularly well suited for application by pad transfer.
A further object of the invention is to provide a quick curing ink for use on a game ball, such as a golf ball, and on hard surfaces of other sporting goods, thereby enabling more rapid production.
Another object of the invention is to provide a pad printable, UV curable ink having good impact resistance.
Yet another object of the invention is to provide a game ball, such as a golf ball, having a clear and durable ink image printed thereon.
A further object of the invention is to provide a method for pad printing an indicia on a hard surface of a game ball, golf club, bat or racket, the indicia comprising a UV curable ink.
Yet another object of the invention is to provide a method for applying a smudge resistant and durable indicia to a visible surface of a game ball.
Other objects of the invention will be in part obvious and in part pointed out more in detail hereafter.
The invention in a preferred form is a game ball with a surface and an indicia comprising a UV curable ink adhered to the surface, the UV curable ink containing aluminum trihydroxide. The impact resistance of the ink and the adhesion between the indicia and the surface are sufficient to render the game ball suitable for use in competitive play.
The indicia can be applied directly to the cover of a one-piece, two-piece or multi-piece game ball. Alternatively, one or more primer coats can be positioned between the game ball cover and indicia. Furthermore, one or more top coats are positioned over the indicia. The indicia is sufficiently durable that after the game ball is subjected to the wet barrel durability test procedure described below, at least about 50%, preferably at least about 70%, and more preferably at least about 80% of the surface area of the original image remains on the game ball.
Another preferred form of the invention is a UV curable ink composition. The ink composition comprises a UV curable resin, aluminum trihydroxide in an amount appropriate to provide the ink composition with improved pad transfer, a coloring agent, such as a pigment or dye, and a photoinitiator for initiating polymerization of the UV curable resin. The ink composition forms a cured indicia having adhesive properties and impact resistance which render the cured indicia suitable for use on game balls to be used in competitive play. A thinning agent which includes a monomer and/or solvent also is preferably included. A wetting agent and/or extender pigment also can be added. To facilitate pad transfer, the ink has a viscosity of 1,000-28,000 centipoise, preferably 1,000-4,000 centipoise, and more preferably 1,000-2,000 centipoise at the time of application.
Yet another preferred form of the invention is a method of applying an indicia to a game ball. The method comprises the steps of (a) obtaining a UV curable ink composition containing a coloring agent, such as a pigment or dye, aluminum trihydroxide, a photoinitiator, and a UV curable resin, the ink composition having a viscosity of 1,000-28,000 and preferably 1,000-4,000 centipoise, (b) applying the ink composition to the game ball in the form of the indicia, (c) curing the ink composition to form a cured film, and (d) applying a coating over the ink. The indicia has an impact resistance sufficient to render the game ball suitable for use in competitive play. The ink preferably is applied by pad printing. The step of UV curing preferably includes placing the indicia under a UV lamp at conditions of lamp intensity, lamp distance and time sufficient to commence curing of the ink. Curing preferably is substantially complete within about 1 second. The fully cured ink preferably, but not necessarily, has a sward hardness (ASTM-D 21 34-66) of 14-40.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others and the article possessing the features, properties, and the relation of elements exemplified in the following detailed disclosure.